It’s a perennial problem with all major FOSS projects and KDE is massive, it’s basically a given. At the time I followed it a bit more closely, there was clearly a churn of developers very similar to what JWZ described, with constant rewrites of entire applications because nobody had the time and inclination to maintain old ones (maintaining other people’s code is hard). Yes, the associated entities do a lot of good work, but it’s never enough - and realistically, nowhere near enough to be responsible for the entire Qt library.